linux-hardening - Re: [PATCH v3] um: refactor deprecated strncpy to memcpy

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Date:   Thu, 10 Aug 2023 12:05:03 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        linux-hardening@...r.kernel.org, linux-um@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] um: refactor deprecated strncpy to memcpy

On Wed, Aug 09, 2023 at 06:19:32PM +0000, Justin Stitt wrote:
> Use `memcpy` since `console_buf` is not expected to be NUL-terminated
> and it more accurately describes what is happening with the buffers
> `console_buf` and `string` as per Kees' analysis [1].
> 
> Also mark char buffer as `__nonstring` as per Kees' suggestion [2].
> 
> This change now makes it more clear what this code does and that
> `console_buf` is not expected to be NUL-terminated.
> 
> Link: https://lore.kernel.org/all/202308081708.D5ADC80F@keescook/ [1]
> Link: https://github.com/KSPP/linux/issues/90 [2]
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
> Cc: linux-hardening@...r.kernel.org
> Suggested-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Thanks for digging through this!

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook